Nuclear reactor system, transmitter device therefor, and associated method of measuring a number of environmental conditions

ABSTRACT

A transmitter device includes a neutron detector structured to generate electrical current from neutron flux, an oscillator circuit having an electrostatic switch electrically connected to the neutron detector, and an antenna electrically connected with the electrostatic switch. The oscillator circuit is structured to pulse the antenna. The antenna is structured to emit a signal corresponding to a number of characteristic values of the oscillator circuit.

BACKGROUND Field

The disclosed concept pertains generally to nuclear reactor systems. Thedisclosed concept also pertains to transmitter devices for nuclearreactor systems. The disclosed concept further pertains to methods ofmeasuring environmental conditions with a transmitter device.

Background Information

In many state-of-the-art nuclear reactor systems in-core sensors areemployed for measuring the radioactivity within the core at a number ofaxial elevations. These sensors are used to measure the radial and axialdistribution of the power inside the reactor core. This powerdistribution measurement information is used to determine whether thereactor is operating within nuclear power distribution limits. Thetypical in-core sensor used to perform this function is a self-powereddetector that produces an electric current that is proportional to theamount of fission occurring around it. This type of sensor does notrequire an outside source of electrical power to produce the current andis commonly referred to as a self-powered detector and is more fullydescribed in U.S. Pat. No. 5,745,538, issued Apr. 28, 1998, and assignedto the Assignee of this invention. FIG. 1 provides a diagram of themechanisms that produce the current I(t) in a self-powered detectorelement 10. A neutron sensitive material such a vanadium is employed forthe emitter element 12 and emits electrons in response to neutronirradiation. Typically, the self-powered detectors are grouped withininstrumentation thimble assemblies. A representative in-coreinstrumentation thimble assembly 16 is shown in FIG. 2. The signal levelgenerated by the essentially non-depleting neutron sensitive emitter 12shown in FIG. 1 is low, however, a single, full core length neutronsensitive emitter element provides an adequate signal without complexand expensive signal processors. The proportions of the full lengthsignal generated by the single neutron sensitive emitter elementattributable to various axial regions of the core are determined fromapportioning the signal generated by different lengths of gammasensitive elements 14 which define the axial regions of the core and areshown in FIG. 2. The apportioning signals are ratioed which eliminatesmuch of the effects of the delayed gamma radiation due to fissionproducts. The in-core instrumentation thimble assemblies also include athermocouple 18 for measuring the temperature of the coolant exiting thefuel assemblies. The electrical signal output from the self-powereddetector elements and the thermocouple in each in-core instrumentationthimble assembly in the reactor core are collected at the electricalconnector 20 and sent to a location well away from the reactor for finalprocessing and use in producing the measured core power distribution.

FIG. 3 shows an example of a core monitoring system presently offeredfor sale by Westinghouse Electric Company LLC, Cranberry, Pa., with aproduct name WINCISE™ that employs fixed in-core instrumentation thimbleassemblies 16 within the instrument thimbles of the fuel assemblieswithin the core to measure the core's power distribution. Cabling 22extends from the instrument thimble assemblies 16 through thecontainment seal table 24 to a single processing cabinet 26 where theoutputs are conditioned, digitized and multiplexed and transmittedthrough the containment walls 28 to a computer workstation 30 where theycan be further processed and displayed. The thermocouple signals fromthe in-core instrumentation thimble assemblies are also sent to areference junction unit 32 which transmits the signals to an inadequatecore cooling monitor 34 which communicates with the plant computer 36which is also connected to the workstation 30. Because of the hostileenvironment within the containment walls 28, the signal processingcabinet 26 has to be located a significant distance away from the coreand the signal has to be sent from the detectors 16 to the signalprocessing cabinet 26 through specially constructed cables that areextremely expensive and the long runs reduce the signal to noise ratio.Unfortunately, these long runs of cable have proved necessary becausethe electronics for signal processing has to be shielded from the highlyradioactive environment surrounding the core region.

In previous nuclear plant designs, the in-core detectors entered thereactor vessel from the lower hemispherical end and entered the fuelassemblies' instrument thimble from the bottom fuel assembly nozzle. Inat least some of the current generation of nuclear plant designs, suchas the AP1000 nuclear plant, the in-core monitoring access is located atthe top of the reactor vessel, which means that during refueling allin-core monitoring cabling will need to be removed before accessing thefuel. A wireless in-core monitor that is self-contained within the fuelassemblies and wirelessly transmits the monitored signals to a signalreceiver positioned inside the reactor vessel but away from the fuelwould allow immediate access to the fuel without the time-consuming andexpensive process of disconnecting, withdrawing and storing the in-coremonitoring cables before the fuel assemblies could be accessed, andrestoring those connections after the refueling process is complete. Awireless alternative would thus save days in the critical path of arefueling outage. A wireless system also allows every fuel assembly tobe monitored, which significantly increases the amount of core powerdistribution information that is available.

However, a wireless system requires that electronic components belocated at or near the reactor core where gamma and neutron radiationand high temperatures would render semi-conductor electronics inoperablewithin a very short time. Vacuum tubes are known to be radiationinsensitive, but their size and electric current demands have made theiruse impractical until recently. Recent developments inmicro-electromechanical devices have allowed vacuum tubes to shrink tointegrated circuit component sizes and significantly reduce power drawdemands. Such a system is described in U.S. patent application Ser. No.12/986,242, entitled “Wireless In-core Neutron Monitor,” filed Jan. 7,2011. The primary electrical power source for the signal transmittingelectrical hardware for the embodiment disclosed in the afore-notedpatent application is a rechargeable battery shown as part of anexemplary power supply. The charge on the battery is maintained by theuse of the electrical power produced by a dedicated power supplyself-powered detector element that is contained within the power supply,so that the nuclear radiation in the reactor is the ultimate powersource for the device and will continue so long as the dedicated powersupply self-powered detector element is exposed to an intensity ofradiation experienced within the core.

Accordingly, one object of this disclosed concept is to provide amechanism to transmit data of environmental conditions within a fuel rodof a fuel assembly to a remote location.

SUMMARY

These needs and others are met by the disclosed concept, which aredirected to an improved nuclear reactor system, transmitter devicetherefor, and associated method of measuring a number of environmentalconditions.

As one aspect of the disclosed concept, a transmitter device isprovided. The transmitter device includes a neutron detector structuredto generate electrical current from neutron flux, an oscillator circuithaving an electrostatic switch electrically connected to the neutrondetector, and an antenna electrically connected with the electrostaticswitch. The oscillator circuit is structured to pulse the antenna. Theantenna is structured to emit a signal corresponding to a number ofcharacteristic values of the oscillator circuit.

As another aspect of the disclosed concept, a nuclear system isprovided. The nuclear reactor system includes a fuel assembly having afuel rod, and the aforementioned transmitter device. The neutrondetector is located in the fuel rod.

As another aspect of the disclosed concept, a method of measuring anumber of environmental conditions with the aforementioned transmitterdevice is provided. The method includes the steps of generating anelectrical current with a neutron detector, storing energy in acapacitor until a trigger voltage of an electrostatic switch of anoscillator circuit is reached, and emitting a signal with an antennacorresponding to a number of characteristic values of the oscillatorcircuit.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic representation of a self-powered radiationdetector;

FIG. 2A is a plan view of an in-core instrument thimble;

FIG. 2B is a schematic view of the interior of the forward sheath of thein-core instrument thimble assembly of FIG. 2A;

FIG. 2C is a sectional view of the electrical connector at the rear endof the in-core instrument thimble assembly of FIG. 2A;

FIG. 3 is a schematic layout of an in-core monitoring system;

FIG. 4 is a simplified schematic of a nuclear reactor system;

FIG. 5 is an elevational view, partially in section, of a nuclearreactor vessel and interior components;

FIG. 6 is an elevational view, partially in section, of a nuclear fuelassembly that contains an in-core nuclear instrument thimble assembly;

FIG. 7 is a schematic, partially cutaway, view of an electrostaticswitch, in accordance with one non-limiting embodiment of the disclosedconcept;

FIG. 8 is an enlarged schematic view of a portion of the electrostaticswitch of FIG. 7;

FIG. 9 is a schematic circuitry diagram of a transmitter device,including the electrostatic switch of FIGS. 7 and 8, in accordance withone non-limiting embodiment of the disclosed concept;

FIG. 10 is a graph showing voltage at a location in the transmitterdevice of FIG. 9 versus time;

FIG. 11 is a graph showing voltage at another location in thetransmitter device of FIG. 9 versus time;

FIG. 12 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept;

FIG. 13 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept; and

FIG. 14 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The primary side of nuclear power generating systems which are cooledwith water under pressure comprises a closed circuit which is isolatedfrom and in heat exchange relationship with a secondary side for theproduction of useful energy. The primary side comprises the reactorvessel enclosing a core internal structure that supports a plurality offuel assemblies containing fissile material, the primary circuit withinheat exchange steam generators, the inner volume of a pressurizer, pumpsand pipes for circulating pressurized water; the pipes connecting eachof the steam generators and pumps to the reactor vessel independently.Each of the parts of the primary side comprising a steam generator, apump and a system of pipes which are connected to the reactor vesselform a loop of the primary side.

For the purpose of illustration, FIG. 4 shows a simplified nuclearreactor system, including a generally cylindrical pressure vessel 40,having a closure head 42 enclosing a nuclear core 44. A liquid reactorcoolant, such as water, is pumped into the vessel 40 by pump 46 throughthe core 44 where heat energy is absorbed and is discharged to a heatexchanger 48, typically referred to as a steam generator, in which heatis transferred to a utilization circuit (not shown), such as a steamdriven turbine generator. The reactor coolant is then returned to thepump 46 completing the primary loop. Typically, a plurality of theabove-described loops are connected to a single reactor vessel 40 byreactor coolant piping 50.

An exemplary reactor design to which this invention can be applied isillustrated in FIG. 5. In addition to the core 44 comprised of aplurality of parallel, vertical, co-extending fuel assemblies 80, forpurpose of this description, the other vessel internal structures can bedivided into the lower internals 52 and the upper internals 54. Inconventional designs, the lower internals' function is to support, alignand guide core components and instrumentation as well direct flow withinthe vessel. The upper internals 54 restrain or provide a secondaryrestraint for the fuel assemblies 80 (only two of which are shown forsimplicity in this figure), and support and guide instrumentation andcomponents, such as control rods 56. In the exemplary reactor shown inFIG. 5, coolant enters the reactor vessel 40 through one or more inletnozzles 58, flows down through an annulus between the reactor vessel 40and the core barrel 60, is turned 180° in a lower reactor vessel plenum61, passes upwardly through a lower support plate and a lower core plate64 upon which the fuel assemblies 80 are seated, and through and aboutthe assemblies. In some designs, the lower support plate 62 and thelower core plate 64 are replaced by a single structure, the lower coresupport plate that has the same elevation as 62. Coolant exiting thecore 44 flows along the underside of the upper core plate 66 andupwardly and through a plurality of perforations 68 in the upper coreplate 66. The coolant then flows upwardly and radially to one or moreoutlet nozzles 70.

The upper internals 54 can be supported from the vessel or the vesselhead 42 and includes an upper support assembly 72. Loads are transmittedbetween the upper support assembly 72 and the upper core plate 66primarily by a plurality of support columns 74. Each support column isaligned above a selected fuel assembly 80 and perforations 68 in theupper core plate 66.

The rectilinearly movable control rods 56 typically include a driveshaft 76 and a spider assembly 78 of neutron poison rods that are guidedthrough the upper internals 54 and into aligned fuel assemblies 80 bycontrol rod guide tubes 79.

FIG. 6 is an elevational view represented in vertically shortened form,of a fuel assembly being generally designated by reference character 80.The fuel assembly 80 is the type used in a pressurized water reactor,such as the reactor of FIG. 5, and has a structural skeleton which atits lower end includes a bottom nozzle 82. The bottom nozzle 82 supportsthe fuel assembly on the lower core support plate 64 in the core regionof the nuclear reactor. In addition to the bottom nozzle 82, thestructural skeleton of the fuel assembly 80 also includes a top nozzle84 at its upper end and a number of guide tubes or thimbles 86 whichextend longitudinally between the bottom and top nozzles 82 and 84 andat opposite ends are rigidly attached thereto.

The fuel assembly 80 further includes a plurality of transverse grids 88axially spaced along and mounted to the guide thimbles 86 (also referredto as guide tubes) and an organized array of elongated fuel rods 90transversely spaced and supported by the grids 88. Although it cannot beseen in FIG. 6, the grids 88 are conventionally formed from orthogonalstraps that are interleaved in an egg-crate pattern with the adjacentinterface of four straps defining approximately square support cellsthrough which the fuel rods 90 are supported in transversely spacedrelationship with each other. In many conventional designs, springs anddimples are stamped into the opposing walls of the straps that form thesupport cells. The springs and dimples extend radially into the supportcells and capture the fuel rods therebetween; inserting pressure on thefuel rod cladding to hold the rods in position. Also, the assembly 80has an instrumentation tube 92 located in the center thereof thatextends between and is mounted to the bottom and top nozzles 82 and 84.With such an arrangement of parts, the fuel assembly 80 forms anintegral unit capable of being conveniently handled without damaging theassembly of parts.

As mentioned above, the fuel rods 90 in the array thereof in theassembly 80 are held in spaced relationship with one another by thegrids 88 spaced along the fuel assembly length. Each fuel rod 90includes a plurality of nuclear fuel pellets 94 and is closed at itsopposite ends by upper and lower end plugs 96 and 98. The fuel pellets94 are maintained in a stack by a plenum spring 100 disposed between theupper end plug 96 in the top of the pellet stack. The fuel pellets 94,composed of fissile material, are responsible for creating the reactivepower of the reactor. The cladding, which surrounds the pellets,functions as a barrier to prevent fission byproducts from entering thecoolant and further contaminating the reactor system.

To control the fission process, a number of control rods 56 arereciprocally movable in the guide thimbles 86 located at predeterminedpositions in the fuel assembly 80. Specifically, a rod cluster controlmechanism (also referred to as a spider assembly) 78 positioned abovethe top nozzle 84 supports the control rods 56. The rod cluster controlmechanism has an internally threaded cylindrical hub member 102 with aplurality of radially extending flukes or arms 104 that with the controlrods 56 form the spider assembly 78 that was previously mentioned withrespect to FIG. 5. Each arm 104 is interconnected to the control rods 56such that the control mechanism 78 is operable to move the control rodsvertically in the guide thimbles to thereby control the fission processin the fuel assembly 80, under the motor power of control rod driveshafts 76 (shown in FIG. 5) which are coupled to the control rod hubs102, all in a well known manner.

As mentioned above, it is often desirable to transmit data of a numberof environmental conditions within a fuel rod (e.g., one of the fuelrods 90 of the fuel assembly 80) to a remote location. FIGS. 7 and 8show different schematic views of a component of such a device able toperform such a function. Specifically, FIGS. 7 and 8 show differentschematic views of an electrostatic switch 250 that may be employed in atransmitter device (e.g., without limitation, transmitter device 200,shown schematically in FIG. 9). The example electrostatic switch 250includes an A terminal 252, a B terminal 254, a first vane 256electrically connected with the A terminal 252, and a number of othervanes 258,260 electrically connected with the B terminal 254. In oneexample embodiment, the vanes 258,260 form a unitary component made froma single piece of material. Furthermore, it will be appreciated that thefirst vane 256 is configured to be located between the second and thirdvanes 258,260. Referring to FIG. 8, the electrostatic switch 250 furtherincludes a first conductor 262 and a second conductor 264. The firstconductor 262 is electrically connected with the A terminal 252 and thefirst vane 256. The second conductor 264 is electrically connected withthe B terminal 254 and the second and third vanes 258,260. The secondand third vanes 258,260 may be electrically connected with the Bterminal 254 via external wiring (not shown). As will be discussedbelow, the electrostatic switch 250 is structured to move from an OPENposition to a CLOSED position. As shown in FIG. 8, the second conductor264 includes a generally linear portion 266, and the electrostaticswitch includes a bracket (e.g., without limitation, U-shaped bracket268) extending from the linear portion 266. When the electrostaticswitch 250 is in OPEN position, the first conductor 262 is spaced fromthe bracket 268. When the electrostatic switch 250 moves from the OPENposition to the CLOSED position, the first conductor 262 moves intoengagement with the bracket 268.

Referring again to FIG. 7, the electrostatic switch 250 further includesan external housing 272 and a support fiber 274 (shown schematically).In one example embodiment, the external housing 272 iscylindrical-shaped (see, for example, FIG. 8). In one optionalembodiment, the housing 272 and the second and third vanes 258,260 forma unitary component made from a single piece of material. Furthermore,it will be appreciated that the second and third vanes 258,260preferably extend from opposite sides of the housing 272 to proximate amiddle region of the housing 272. Continuing to refer to FIG. 7, it willbe appreciated that the first vane 256 is located internal with respectto the housing 272. Additionally, the support fiber 274 is coupled tothe first vane 256 and the housing 272, and is configured to provide atorsional preload on the first vane 256. However, when the electrostaticswitch 250 moves from the OPEN position to the CLOSED position,electrostatic attractive forces between the first vane 256 and thesecond and third vanes 258,260 overcome the preload of the support fiber274 in order to move the electrostatic switch 250 to the CLOSEDposition.

Additionally, the electrostatic switch 250 has a mechanism to bemaintained in the CLOSED position. Specifically, as shown in FIG. 8, thelinear portion 266 of the second conductor 264 is located substantiallyparallel to the first conductor 262. As such, when the electrostaticswitch is in the CLOSED position, current flows through the firstconductor 262 in a first direction (see arrow in first conductor 262)and through the linear portion 266 of the second conductor 264 in asecond direction (see arrow in linear portion 266) generally oppositethe first direction. As a result, this creates a repulsiveelectromagnetic force between the first conductor 262 and the linearportion 266 of the second conductor 264 in order to maintain theelectrostatic switch 250 in the CLOSED position. Accordingly, as long ascurrent is flowing (e.g., even at relatively low levels), theelectromagnetic repulsive force maintains the electrostatic switch 250in the CLOSED position. The electrostatic switch 250 will not return tothe OPEN position until the repulsive force due to the current dropsbelow the torsional preload of the support fiber 274. This may occurwhen the current drops to near zero amperes. Thus, the electrostaticswitch 250 is closed by electrostatic forces from an applied voltage, ismaintained in the CLOSED position by electromagnetic forces due to thecurrent flowing during closure, and then moves to the OPEN position whenthe current flow drops and the electromagnetic forces dissipate.

Continuing to refer to FIG. 8, in one optional embodiment, theelectrostatic switch 250 further includes a support post 276, acontainer 278, and an electrically conductive substance (not shown)located internal with respect to the container 278. The support post 276is mechanically coupled to the first vane 256 and electrically connectedto the A terminal 252. In this manner, the support post 276advantageously provides structural support for the first vane 256.Furthermore, the first conductor 262 extends from the support post 276.

The container 278, with the electrically conductive substance locatedtherein, electrically connects the support post 276 to the A terminal252. The electrically conductive substance is preferably a fusible metalalloy that is solid at room temperature. In this solid state, thefusible metal alloy in the container 278 provides structural support tothe vanes 256,258,260 to minimize and/or prevent damage duringfabrication and shipping of the electrostatic switch 250. However, inoperation, once the fuel heats up, the fusible metal alloy melts and theelectrostatic switch 250 becomes operational.

When the electrostatic switch 250 is in the OPEN position, the firstvane 256 does not engage either of the second or third vanes 258,260. Inone optional embodiment, when the electrostatic switch 250 is in theOPEN position, the first vane 256 is located substantially parallel toand is spaced from the second and third vanes 258,260. It will beappreciated that in this OPEN position, a torsional preload on thesupport fiber 274, and thus on the first vane 256, maintains theelectrostatic switch 250 in the OPEN position. As will further bediscussed below, when a voltage is applied to the electrostatic switch250, electrostatic forces are developed that attract the first vane 256toward the second and third vanes 258,260. Once this force exceeds thetorsional preload of the support fiber 274, the first vane 256 willbegin to rotate and will cause the electrostatic switch 250 to close.Accordingly, when the electrostatic switch 250 moves from the OPENposition to the CLOSED position, the first vane 256 rotates toward thesecond and third vanes 258,260.

The transmitter device 200, which includes the electrostatic switch 250,will now be discussed in greater detail in connection with FIGS. 9-11.As shown in FIG. 9, the transmitter device 200 includes a self-poweredneutron detector 210, an oscillator circuit 220 electrically connectedto the neutron detector 210, and an antenna 240. The neutron detector210 is configured to be located in one of the fuel rods 90 (FIG. 6). Theexample oscillator circuit 220 includes a capacitor 222, an inductor 224configured to be electrically connected with the capacitor 222, and theelectrostatic switch 250. As shown, the capacitor 222 is electricallyconnected with the neutron detector 210. The electrostatic switch 250 isalso electrically connected to the neutron detector 210 and the antenna240. In operation, the oscillator circuit 220 is structured to pulse theantenna 240, and the antenna 240 is structured to emit a signalcorresponding to a number of characteristic values of the oscillatorcircuit 220, as will be discussed below.

When the transmitter device 200 is located within one of the fuel rods90 (FIG. 6) of the fuel assembly 80 (FIGS. 5 and 6), the neutrondetector 210 is structured to generate an electrical current fromneutron flux. Accordingly, the neutron detector 210, and thus thetransmitter device 200, is advantageously self-powered (i.e., devoid ofa separate powering mechanism). That is, the transmitter device 200 hasonly one single powering mechanism, that powering mechanism being theneutron detector 210. Additionally, the transmitter device 200 isadvantageously devoid of semiconductors. Many known attempts atproviding a wireless mechanism to communicate data on environmentalconditions typically require more power than is available from a neutrondetector, and/or are not able to withstand the relatively harshradiation environment due to the inclusion of semiconductors. In theexample of FIG. 9, the capacitor 222 is electrically connected with theA terminal 252 of the electrostatic switch 250, and the antenna 240 iselectrically connected with the B terminal 254 of the electrostaticswitch 250.

The operation of the transmitter device 200 will now be discussed indetail. When the transmitter device 200 is located in one of the fuelrods 90 (FIG. 6), the neutron detector 210 functions as a current sourcethat charges the capacitor 222. The voltage across the capacitor 222increases as the energy is stored and it continues to climb until atrigger voltage V_(t) (see, for example, FIG. 10) of the electrostaticswitch 250 is reached. See, for example, FIG. 10, wherein voltage V₁ ismeasured at a location of the transmitter device 200 in FIG. 9, and thetrigger voltage V_(t) of the electrostatic switch 250 is a predeterminedvoltage that is reached at this location. As shown, the voltage V₁increases until the trigger voltage V_(t) of the electrostatic switch250 is reached. Once the trigger voltage V_(t) of the electrostaticswitch 250 is reached, the electrostatic switch 250 becomes conductivesuch that the A and B terminals 252,254 electrically connect thecapacitor 222 to the antenna 240. Stated differently, when the triggervoltage V_(t) of the electrostatic switch 250 is reached, theelectrostatic switch 250 moves from the OPEN position to the CLOSEDposition and connects the capacitor 222 to the inductor 224, therebycreating the oscillator circuit 220. This closure by the electrostaticswitch causes a relatively strong oscillation of the oscillator circuit220, which is inherently unstable, for a short period of time. Thedamped oscillation continues until the energy is dissipated byelectromagnetic emissions from the antenna 240 and other losses (e.g.,resistive losses).

FIG. 11 shows a graph of voltage V₂ versus time measured in theoscillator circuit 220. As shown, the voltage V₂ generally begins atzero volts, oscillates for a relatively short period of time, andthereafter returns to zero volts before repeating the cycle. Thedampening of the oscillations is due to energy being dissipated byelectromagnetic emissions from the antenna 240 and resistive losses.Accordingly, the oscillator circuit 220 pulses the antenna 240, whichemits a wireless signal.

It will be appreciated that the period between the pulsed signalsemitted by the antenna 240 corresponds inversely to the neutron fluxdetected by the neutron detector 210. More specifically, the currentgenerated by the neutron detector 210 is directly proportional to theneutron flux within the corresponding fuel rod 90 (FIG. 6), and thetrigger voltage V_(t) of the electrostatic switch 250 is relativelyconstant. As such, the period between pulses (see, for example, t₁ inFIG. 11) is also inversely proportional to the neutron flux within thefuel rod 90 (FIG. 6). Therefore, a suitable wireless receiver receivingthe signal emitted by the antenna 240 can readily be calibrated todetermine the neutron flux within the fuel rod 90 (FIG. 6).Additionally, the energy of the pulsed transmissions of the antenna 240remains essentially the same even if the reactor core power is very low.The pulses simply occur less often. Furthermore, because the frequencyof the transmitter device 200 is independent of pulse operation, adevice designer is able to select the frequency of the transmitterdevice 200. This advantageously facilitates the use of many differenttransmitter devices at different locations in the fuel assembly 80(FIGS. 5 and 6), and in other fuel assemblies in the core. It will beappreciated that the neutron detector 210 and sensors could be locatedat advantageous locations along the height of the fuel assembly 80(FIGS. 5 and 6), whereas the transmitter circuit would generally alwaysbe in the fuel assembly's 80 (FIGS. 5 and 6) top plenum (e.g., any fuelrod or assembly). An operator would be able to identify each individualtransmitter device by its associated frequency, which is dependent onthe values of the capacitance of the capacitor 222 and the inductance ofthe inductor 224. Accordingly, environmental conditions such as neutronflux are advantageously able to be monitored wirelessly at manydifferent locations within the fuel assembly 80 (FIGS. 5 and 6).

FIG. 12 shows a schematic circuitry diagram of another transmitterdevice 300, in accordance with another non-limiting embodiment of thedisclosed concept. As shown, the transmitter device 300 is structuredsimilar to the transmitter device 200 (FIG. 9), and like components arelabeled with like reference numbers. For ease of illustration andeconomy of disclosure, only the oscillator circuit 320 and the antenna340 are indicated with reference numbers. However, as shown, theoscillator circuit 320 of the transmitter device 300 further includes aresistance temperature detector 326 electrically connected in serieswith the inductor 324 and electrically connected to the capacitor 322.The resistance temperature detector 326 increases its electricalresistance as the temperature of the environment in which it is locatedincreases. In accordance with one aspect of the disclosed concept, theresistance temperature detector 326 alters the signal emitted by theantenna 340 in a detectable way. More specifically, the amplitude decayrate of the voltage of the oscillator circuit 320 will be altered withthe inclusion of the resistance temperature detector 326. Accordingly,the change in the amplitude decay rate measured by a suitable wirelessreceiver will allow an operator to readily determine a given temperatureat a location within the fuel rod 90 (FIG. 6). It follows that thetransmitter device 300 is advantageously able to provide an indicationto an operator of neutron flux (i.e., in the same manner as thetransmitter device 200 shown in FIG. 9) and also temperature within thefuel rod 90 (FIG. 6).

FIGS. 13 and 14 show schematic circuitry diagrams of two othertransmitter devices 400,500, respectively, in accordance with othernon-limiting embodiments of the disclosed concept. As shown, thetransmitter devices 400,500 are structured similar to the transmitterdevices 200,300 (FIGS. 9 and 12), and like components are labeled withlike reference numbers. For ease of illustration and economy ofdisclosure, only the antennas 440,540 and the oscillator circuits420,520 are identified with reference numbers. As shown in FIG. 13, theoscillator circuit 420 further includes a second inductor (e.g., withoutlimitation, variable inductor 428) electrically connected in series withthe first inductor 424 and the resistance temperature detector 426. Asshown in FIG. 14, the oscillator circuit 520 further includes a variablecapacitor 528 electrically connected in parallel with the firstcapacitor 522. The variable capacitor 528 is also electrically connectedto the inductor 524 and the resistance temperature detector 526.Advantageously, environmentally induced changes in the electrical valuesof either the variable inductor 428 or the variable capacitor 528 willproduce a detectable shift in the pulse transmission frequency.

It will be appreciated that the transmitter devices 400,500 areadvantageously able to provide an indication to an operator of up tothree environmental conditions within the fuel rods 90 (FIG. 6). Forexample, the transmitter devices 400,500 each, via the emitted signalsof the respective antennas 440,540, are each able to communicate to awireless receiver data corresponding to the neutron flux and thetemperature within the fuel rod 90 (FIG. 6) in the same manner as thetransmitter device 300, discussed above. Additionally, the variableinductor 428 (FIG. 13) and the variable capacitor 528 (FIG. 14) are eachstructured to alter the frequency of the emitted signal of therespective antennas 440,540 in a detectable way. The altered frequencyprovides a mechanism by which a third environmental condition (e.g.,without limitation, pressure, total neutron dose of a fuel rod overtime, water flow rate) can be measured by the transmitter devices400,500 and reported wirelessly to a suitable receiver. For example, thepressure within a fuel rod may create a deformation that causes amovement near a coil of the variable inductor 428 to cause a detectablefrequency shift in the emitted signal of the antenna 440, thus allowingthe pressure to be monitored wirelessly.

It will be appreciated that a method of measuring a number ofenvironmental conditions with one of the transmitter devices200,300,400,500 includes the steps of generating an electrical currentwith the neutron detector 210, storing energy in the capacitor222,322,422,522 until a trigger voltage V_(t) of the electrostaticswitch 250 is reached, and emitting a signal with the antenna240,340,440,540 corresponding to a number of characteristic values ofthe oscillator circuit 220,320,420,520. The method may further includealtering the signal emitted by the antenna 340,440,540 with theresistance temperature detector 326,426,526. The method may also furtherinclude altering the signal emitted by the antenna 440 with the secondinductor 428.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

1-17. (canceled)
 18. A method of measuring a number of environmentalconditions with a transmitter device, said transmitter device comprisinga neutron detector structured to generate electrical current fromneutron flux, an oscillator circuit comprising an electrostatic switchelectrically connected to said neutron detector, and an antennaelectrically connected with said electrostatic switch, wherein saidelectrostatic switch is moveable based on said neutron detector, whereinsaid oscillator circuit is structured to pulse said antenna based onsaid neutron detector, wherein a period between pulses is related to theneutron flux, said oscillator circuit further comprising a capacitor andan inductor configured to be electrically connected with said capacitor,said capacitor being electrically connected with said neutron detector,the method comprising the steps of: generating the electrical currentwith said neutron detector; storing energy in said capacitor until atrigger voltage of said electrostatic switch is reached; and emitting asignal with said antenna corresponding to a number of characteristicvalues of said oscillator circuit.
 19. The method of claim 18 whereinsaid oscillator circuit further comprises a resistance temperaturedetector electrically connected in series with said inductor; andwherein the method further comprises: altering the signal emitted bysaid antenna with said resistance temperature detector.
 20. The methodof claim 18 wherein said oscillator circuit further comprises a secondinductor electrically connected in series with said inductor; andwherein the method further comprises: altering the signal emitted bysaid antenna with said second inductor.
 21. The method of claim 20wherein said second inductor is a variable inductor.
 22. The method ofclaim 18 wherein said transmitter device is devoid of a semiconductor.23. The method of claim 18 wherein said electrostatic switch comprises afirst terminal, a second terminal, a first vane electrically connectedwith said first terminal, and at least one other vane electricallyconnected with said second terminal; wherein said capacitor iselectrically connected with one of said first terminal or said secondterminal; and wherein said antenna is electrically connected with theother of said first terminal or said second terminal.
 24. The method ofclaim 23 wherein said electrostatic switch further comprises a firstconductor and a second conductor; wherein said first conductor iselectrically connected with said first terminal and said first vane;wherein said second conductor is electrically connected with said secondterminal and said at least one other vane; wherein said electrostaticswitch is structured to move from an OPEN position to a CLOSED position;wherein said electrostatic switch further comprises a bracket extendingfrom a portion of said second conductor; wherein, when saidelectrostatic switch is in the OPEN position, said first conductor isspaced from said bracket; wherein, when said electrostatic switch movesfrom the OPEN position to the CLOSED position, said first conductormoves into engagement with said bracket.
 25. The method of claim 24wherein said electrostatic switch further comprises a housing and asupport fiber; wherein said first vane is disposed internal with respectto said housing; wherein said support fiber is coupled to said firstvane and said housing and is configured to provide a torsional preloadon said first vane; wherein, when said electrostatic switch moves fromthe OPEN position to the CLOSED position, electrostatic attractiveforces between said first vane and said at least one other vane overcomethe preload of said support fiber in order to move said electrostaticswitch to the CLOSED position.
 26. The method of claim 24 wherein saidportion of said second conductor is disposed substantially parallel tosaid first conductor; wherein, when said electrostatic switch is in theCLOSED position, current flows through said first conductor in a firstdirection; and wherein, when said electrostatic switch is in the CLOSEDposition, current flows through said portion of said second conductor ina second direction generally opposite the first direction, therebycreating a repulsive electromagnetic force between said first conductorand said portion of said second conductor in order to maintain saidelectrostatic switch in the CLOSED position.
 27. The method of claim 24wherein said electrostatic switch further comprises a support postmechanically coupled to said first vane and electrically connected tosaid first terminal; and wherein said first conductor extends from saidsupport post.
 28. The method of claim 27 wherein said electrostaticswitch further comprises a container and an electrically conductivesubstance disposed internal with respect to said container; and whereinsaid container electrically connects said support post to said firstterminal.
 29. The method of claim 24 wherein said at least one othervane comprises a second vane and a third vane each electricallyconnected with said second terminal; wherein said first vane is disposedbetween said second vane and said third vane; and wherein, when saidelectrostatic switch moves from the OPEN position to the CLOSEDposition, said first vane rotates toward said second vane and said thirdvane.
 30. The method of claim 29 wherein said second vane and said thirdvane form a unitary component made from a single piece of material. 31.The method of claim 29 wherein, when said electrostatic switch is in theOPEN position, said first vane is disposed parallel to said second vaneand said third vane.
 32. The method of claim 18 wherein said transmitterdevice comprises only one single powering mechanism; and wherein saidone single powering mechanism is said neutron detector.
 33. A method ofmeasuring a number of environmental conditions with a transmitterdevice, said transmitter device comprising a neutron detector structuredto generate electrical current from neutron flux, an oscillator circuitcomprising an electrostatic switch electrically connected to saidneutron detector, and an antenna electrically connected with saidelectrostatic switch, wherein said electrostatic switch is moveablebased on said neutron detector, wherein said oscillator circuit isstructured to pulse said antenna based on said neutron detector, whereina period between pulses is related to the neutron flux, the methodcomprising the steps of: generating the electrical current with saidneutron detector; storing energy in said oscillator circuit until atrigger voltage of said electrostatic switch is reached; and emitting asignal with said antenna corresponding to a number of characteristicvalues of said oscillator circuit.